Drive chains are used to transfer power from a source of rotational energy to a secondary chain or similar device such as the power chain in a power and free conveyor system. The drive chain is connected between two sprockets, at least one of which is powered by a drive shaft, and includes a plurality of teeth or dogs extending outwardly from the chain for engaging the driven chain. The drive chain is positioned in proximity to the driven chain, and a backup bar is used to guide the drive chain and hold it against the driven chain. This allows the teeth on the drive chain to engage the secondary chain and transmit the rotation of the drive chain to the driven chain.
A backup bar must be carefully positioned in order to transfer power from the drive chain to the driven chain in an efficient manner. If the bar does not hold the drive chain sufficiently firmly against the conveyor chain, the teeth may slip, resulting in a lower or inconsistent level of power. If the drive chain is pressed too firmly against the conveyor chain, it may interfere with the smooth rotation of the drive shaft. If the drive chain is not properly aligned with the chain being driven, damage may result to one or both of the chains, shortening the lives thereof. Furthermore, significant stresses are placed on the backup bar by the drive chain during operation which could alter the orientation of the backup bar if it were not securely fastened in place. Therefore, drive chain assemblies are constructed with backup bars bolted in place to hold the drive chain precisely in position.
It occasionally becomes necessary to disengage the drive chain from the conveyor chain such as when performing certain maintenance tasks or when auxiliary drives are connected to the conveyor. In order to do this, it is necessary to unbolt the backup bar and remove it, or reposition it so that it no longer holds the drive chain against the conveyor chain and refasten the backup bar in this new position. Because the unbolting of the backup bar can introduce slack into the drive chain, the person performing this operation must be careful to ensure that the drive chain is completely clear of the conveyor chain and not drooping onto the conveyor or onto any other moving parts. It may also be necessary to secure the drive chain to keep it clear of the conveyor chain. Care must be taken not to operate the drive chain when slack is present because this could cause the drive chain to slip off of the drive sprockets and cause damage to nearby equipment such as the drive shaft. This repositioning process requires a variety of tools and special skills and can take approximately 15 minutes, even when performed by a skilled technician or engineer. It would therefore be desirable to provide a backup bar assembly that could be repositioned quickly to positively engage or disengage a drive chain from a conveyor chain and which could be operated without special tools or skills, yet which was still capable of securely holding a backup bar in a required position.